Liquid Mole Fraction Research Articles

Thermodynamic Analysis of Capillary and Electric Field Effects on Liquid-Vapor Equilibrium: A Study on the Water-Ethanol Mixture.

This study investigates phase equilibrium manipulation in nonideal mixtures through a combined capillary and external electric field approach. Utilizing thermodynamic principles, an expression is established for estimating the equilibrium liquid mole fraction in a confined system subjected to a localized electric field within a capillary that is filled with a liquid phase in equilibrium with its vapor counterpart. Applied to a water-ethanol system, the model suggests large shifts in the equilibrium liquid mole fraction of water due to the electric field and capillary effects. These findings reveal that while the capillary's influence remains negligible for radii exceeding 10 nm, capillaries of smaller dimensions, when exposed to electric fields of around 300 MV/m, can amplify the equilibrium liquid water mole fraction by up to 55%. This suggests the potential for phase equilibrium control through larger capillaries and lower electric fields, while intriguing complexities arise at very small radii.

Modeling of the Vapor-Liquid Equilibria Properties of Binary Mixtures for Refrigeration Machinery

The presence of both critical and azeotropic states in the vapor-liquid equilibria (VLE) is a very important issue in the chemical and refrigeration engineering. The knowledge of the phase behavior (subcritical phase/supercritical phase) of refrigerant allows designing and optimizing the refrigeration industrials processes. However, it is rare to find data for this information, which poses a great challenge for researchers to develop predictive and correlative thermodynamic models. The present study proposes the computation of the compositions and pressures of critical and azeotropic points of the isothermal VLE as well as the correlation of experimental VLE data. Firstly, experimental data (PTxy) was used to predict the vapor-liquid phase of both critical and azeotropic behaviors and to determine their properties using the relative volatility model. Secondly, the thermodynamic model (PR-MC-WS-NRTL) was applied to correlate the data of the binary refrigerant systems and describe their isothermal (VLE) behavior. The results proved that there is good agreement between predicted values obtained by the developed model and the experimental reference data. The relative error of both critical and azeotropic properties does not exceed 4.3 % for the molar fraction and 7.5 % for the pressure using relative volatility model. On other hand the relative deviation is respectively less than 2.60 % and 2.58 % for the liquid and vapor mole fractions using (PR-MC-WS-NRTL) model. This shows the ability of these models to give a reliable solution to predict and modulate the phase behavior of the binary refrigerant systems.

Exploring the Microscopic Aspects of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Formamide, N-Methylformamide, and N,N-Dimethylformamide by Multiple Spectroscopic Techniques and Computations.

The microscopic aspects of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) mixtures with formamide (FA), N-methylformamide (NMF), and N,N-dimethylformamide (DMF) were investigated using spectroscopic techniques of femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), FT-IR, and NMR. Molecular dynamics simulations and quantum chemistry calculations were also performed. According to fs-RIKES, the first moment of the low-frequency spectrum bands mainly originating from the intermolecular vibrations in the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems changed gradually with the molecular liquid mole fraction XML but that in the [MOIm][BF4]/NMF system was constant up to XNMF = 0.7 and then gradually increased in the range of XNMF ≥ 0.7. Excluding the contribution of the 2D hydrogen-bonding network due to the presence of FA in the low-frequency spectrum band, the XML dependence of the normalized first moment of the low-frequency band in the [MOIm][BF4]/FA and [MOIm][BF4]/NMF systems revealed that the normalized first moment did not remarkably change in the range of XML < 0.7 but drastically increased in XML ≥ 0.7. FT-IR results indicated that the amide C═O band shifted to the low-frequency side with increasing XML for the three mixtures due to the hydrogen bonds. The imidazolium ring C-H band also showed a similar tendency to the amide C═O band. 19F NMR probed the microenvironment of [BF4]- in the mixtures. The [MOIm][BF4]/NMF and [MOIm][BF4]/DMF systems showed an up-field shift of the F atoms of the anion with increasing XML, and the [MOIm][BF4]/FA system exhibited a down-field shift. Steep changes in the chemical shifts were confirmed in the region of XML > 0.8. On the basis of the quantum chemistry calculations, the observed chemical shifts with increasing XML were mainly attributed to the many-body interactions of ions and amides for the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems. Meanwhile, the long distance between the cation and the anion was due to the high dielectric medium for the [MOIm][BF4]/NMF system, which led to an up-field shift.

Formation of robust CEI film on high voltage LiNi0.6Co0.2Mn0.2O2 cathode enabled by functional [PIVM][TFSA] ionic liquid additive

• A novel multifunctional ionic liquid was designed and synthesized using a two-step method. • Physicochemical properties of the new ionic liquid with DMC and EMC were investigated. • The cycle performance and rate properties were enhanced by adding an ionic liquid additive. • The mechanisms were determined by CV, SEM and XPS analysis techniques. The ionic liquid 1-(3-amino-3-oxopropyl)-3-vinylimidazolium bis(trifluoromethylsulfonyl)amide ([PIVM][TFSA]) was synthesized and applied in the electrolyte of Li/LiNi 0.6 Co 0.2 Mn 0.2 O 2 lithium ion batteries. The thermostability of this pure ionic liquid was investigated to provide a wide liquid range from -50 ℃ to 200 ℃. The physicochemical properties of binary mixtures of this ionic liquid with DMC and EMC were measured at different temperatures and with different ionic liquid mole fractions. [PIVM][TFSA] widens the electrochemical window of the electrolyte. The ionic liquid inhibits the increasing of water and HF content in the electrolyte. A comparison of charge and discharge performances in different electrolytes with various content of ionic liquid is reported. The electrolyte with the concentration of 1.0 wt % [PIVM][TFSA] has the best electrochemical properties. It enhances the initial capacity, the capacity retention and the high current rate performance of the cells. The surface film on the electrodes was confirmed by SEM and XPS that the ionic liquid [PIVM][TFSA] participated in membrane formation and played an active role.

Experimental measurements and modelling of vapour−liquid equilibria for four mixtures of 2,3,3,3−tetrafluoropropene (R1234yf) with 1,1,1,2−tetrafluoroethane (R134a) or 1,1−difluoroethane (R152a) or trans−1−chloro−3,3,3−trifluoropropene (R1233zd(E)) or 2−chloro−3,3,3−trifluoropropene (R1233xf)

Isothermal vapour−liquid equilibrium (VLE) for four binary systems involving R1234yf (R1234yf + R134a, R1234yf + R152a, R1234yf + R1233zd(E) and R1234yf + R1233xf) were measured at temperatures from 278.15 to 348.15 K. The experiments were conducted by means of a “static−analytic” apparatus with phase analysis via gas chromatography, with resulting uncertainties of 0.6 K for temperature, 8 kPa for pressure and a maximum of 0.007 for vapour and liquid mole fractions. The main advantage of the equipment is that vapour and liquid samples are taken from vapour and liquid phases by two capillary samplers (ROLSI®). The Peng Robinson Equation of State is considered to represent the experimental data. If possible, comparison between the new experimental data and prediction with REFPROP 10.0 software are realized.

Liquid – liquid equilibria in binary and ternary systems of phenol + hydrocarbons (n–dodecane or n–hexadecane) and water + phenol + hydrocarbons (n–dodecane or n–hexadecane) at temperatures between 298K and 353K

This study reports liquid–liquid equilibrium (LLE) and liquid–liquid–liquid equilibrium (LLLE) data for binary (phenol + n-dodecane, or n-hexadecane) and ternary (water + phenol + n-dodecane, or n-hexadecane) systems measured under atmospheric pressure. The compositions of coexisting phases were determined with analytical and cloud point methods at temperatures 298 K – 353 K. The Non–Random Two–Liquid (NRTL) excess Gibbs energy model was employed to correlate the measured systems. The binary interaction parameters were regressed using analytical LLE and cloud point data. In addition, the parameters were also calculated using the binary LLE data combined with the isothermal vapor–liquid data from the literature applying the NRTL–RK (Redlich–Kwong) property method. The average absolute deviations in liquid mole fraction obtained with the NRTL model (using six adjusted parameters) for the LLE and VLE experimental data were 0.006 and 0.014 respectively. The phase equilibria of binary phenol + hydrocarbon (n-dodecane or n-hexadecane) systems were modeled at the temperature range of 313 K – 573 K.

Experimental investigation on the phase behavior of DME/ [P6,6,6,14][Cl] and thermodynamic analysis for absorption refrigeration system

Dimethyl ether (DME), as an environmental-friendly alternative refrigerant, has received broadly attention. Phosphonium-based ionic liquids with good thermophysical properties are regarded as promising absorbents in absorption refrigeration systems. In this work, the measurement of solubility behavior to DME in trihexyltetradecylphosphonium chloride ([P6,6,6,14][Cl]) was carried out from 278.15 K to 348.15 K by means of isochoric saturation method. Non-random two liquid (NRTL) model and Krichevsky-Kasarnovsky (K-K) model were used to correlate the experimental data. The absolute average relative deviation between experimental liquid mole fraction and calculated values was 0.739% and 1.517% for NRTL model and K-K model respectively. Based on the solubility results, the performance of single-effect absorption refrigeration cycle used DME/[P6,6,6,14][Cl] pairs was analyzed, and further compared with other working pairs composed of [P6,6,6,14][Cl].

Liquid Density Prediction of Ethanol/Water, Using Artificial Neural Network

In this work, our objective was to get a reliable model for predicting liquid density ethanol-water and use it again later in modeling the ethanol production process from biomass. Hence, the unreliability of the Peng-Robinson equation of state to predict this property was shown. The average absolute deviation of this prediction is equal to 14.72 %. To have a reliable model, an artificial neural network (ANN) method was followed. Levenberg–Marquardt algorithm is used to choose the optimized ANN structure that has ten neurons in the hidden layer, three neurons in the input layer, and one neuron in the output layer, with a tangent-sigmoid and linear transfer functions, in the hidden and the output layers, respectively. The model training was done using 348 experimental data points from published experiments, realized at different liquid mole fraction range, pressure (0.10 to 10.00MP), and temperature (298.15 K to 476.2 K). The correlation coefficient between the experimental and liquid phase density was 0.9999 for training, validation, and testing the model. Statistical analysis is employed to evaluate the accuracy of the ANN, showing that the average absolute deviation, root mean square, and the Bias are 0.047 %, 0.003 %, and -0.004 %, respectively. So the ANN model gives a good estimation of liquid density, for mixture ethanol/water, with a relative importance of pressure, composition, and temperature equal to 41%, 34 %, and 25 %, respectively.

A novel modification of ionic liquid mixture density based on semi-empirical equations using laplacian whale optimization algorithm

The main motivation of this study is development of density prediction of mixture including ionic liquid (IL) using semi-empirical and cubic equations of state (CEoS). The considered systems are contained of 51 ILs, 41 solvents and 4626 data point in the wide temperature range (278.15–348.15 K), ionic liquid mole fraction (0.0040–0.9977) and atmospheric pressure. Six simple semi-empirical equations with different mixing rules and two CEoSs (Soave-Redlich-Kwong EoS and Patel-Teja EoS) is investigated to predict the IL-mixture density. For each semi-empirical equation, the coefficients are optimized using laplacian whale optimization algorithm based on cation-family. These generalized modifications have not been used to ILs beforehand consequently, the accuracy and appropriateness of these equations to predict IL-mixture density are unsknown until now. The obtained results based on semi-empirical equations indicate that the performed modification provides low deviation of experimental data and can be applied by confidence in engineering and thermodynamic calculations. However, the results based on two CEoS show inacceptable accuracy.

Vapor pressures and vapor phase compositions of choline chloride urea and choline chloride ethylene glycol deep eutectic solvents from molecular simulation.

Despite the widespread acknowledgment that deep eutectic solvents (DESs) have negligible vapor pressures, very few studies in which the vapor pressures of these solvents are measured or computed are available. Similarly, the vapor phase composition is known for only a few DESs. In this study, for the first time, the vapor pressures and vapor phase compositions of choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs are computed using Monte Carlo simulations. The partial pressures of the DES components were obtained from liquid and vapor phase excess Gibbs energies, computed using thermodynamic integration. The enthalpies of vaporization were computed from the obtained vapor pressures, and the results were in reasonable agreement with the few available experimental data in the literature. It was found that the vapor phases of both DESs were dominated by the most volatile component (hydrogen bond donor, HBD, i.e., urea or ethylene glycol), i.e., 100% HBD in ChClEg and 88%-93% HBD in ChClU. Higher vapor pressures were observed for ChClEg compared to ChClU due to the higher volatility of ethylene glycol compared to urea. The influence of the liquid composition of the DESs on the computed properties was studied by considering different mole fractions (i.e., 0.6, 0.67, and 0.75) of the HBD. Except for the partial pressure of ethylene glycol in ChClEg, all the computed partial pressures and enthalpies of vaporization showed insensitivity toward the liquid composition. The activity coefficient of ethylene glycol in ChClEg was computed at different liquid phase mole fractions, showing negative deviations from Raoult's law.

Ionic liquid excess molar volume prediction: A conceptual comparison

In this study, the prediction of excess molar volume of ionic liquid + solvent binary system is described using modified two-parameter and three-parameter cubic equation of state (CEoS). The studied binary systems are consisted of 41 ionic liquids, 40 solvents and 5293 data point in the wide temperature range (278.15–353.15 K), ionic liquid mole fraction (0.0036–0.9920) and atmospheric pressure i.e. P = 1 bar. At the first step, the volume-translated parameter (c) was obtained based on three linear, distance function and exponential-type temperature-dependent cases and using experimental pure density. After that, and due to easy-to-use of c-parameter, various formula was presented based on pure component thermodynamic features for all three cases (IL and solvent, separately). Finally, to investigate the accuracy of presented c-parameter formula, the excess molar volume of 119 various binary systems was molded using volume-translated PR (VTPR) EoS and volume-translated SRK (VTSRK) EoS without using any binary interaction parameter and the obtained results was compared with the original three-parameter CEoS, Patel-Teja (PT) EoS. The obtained results indicated that the performed two-parameter CEoS modification leads to increase the accuracy of the conventional PR EoS and SRK EoS in comparision to original two-parameter CEoS version and also, PT EoS. The average absolute percent deviation of the VTSRK EoS (c-parameter based on distance function) and the VTPR EoS (c-parameter based on exponential-type temperature-dependent volume-translated) were fewer values through all studied cases and it was 2.0443 and 2.8927, respectively.

PVT properties of binary systems of diisopropylethylammonium octanoate ionic liquid with oligomeric polyethylene glycol or polypropylene glycol at elevated pressures

The densities were measured for two binary systems of protic ammonium-based ionic liquid, diisopropylethylammonium octanoate ([DIPEA][C7COO]), with oligomeric polyethylene glycol (PEG-200) or polypropylene glycol (PPG-425) at temperatures from 298.2 K to 348.2 K and pressures up to 50 MPa. Tait equation was used to represent the pressure-dependence of the liquid densities and then applied to estimate the isothermal compressibilities. The excess molar volumes of [DIPEA][C7COO] + PEG-200 are negative over the entire composition range, while those of [DIPEA][C7COO] + PPG-425 varying with the mole fraction of the ionic liquid are S-shape changing from positive to negative. While the excess volumes were fitted to a modified Redlich-Kister equation, the density data were correlated with a generalized equation and with the Flory-Orwoll-Vrij (FOV) and the Schotte equations of state.

Measurement of phase equilibrium and interfacial tension for the (1-propanol + cyclopentyl methyl ether) binary mixture

Vapour – liquid equilibrium and interfacial tension for 1-propanol + cyclopentyl methyl ether binary mixture have been experimentally measured in the whole mole fraction range. Vapour – liquid equilibrium determinations have been carried out in an all-glass dynamic Guillespie cell over the temperature range from 352.7 K to 375.8 K at three isobaric conditions 50, 75, and 94 kPa. interfacial tension has been measured using a maximum differential bubble pressure tensiometer at 298.15 K and 101.33 kPa.According to the experimental results of vapour – liquid equilibrium, the 1-propanol + cyclopentyl methyl ether binary mixture presents positive deviation from the ideal behaviour with a minimum temperature azeotropic over the whole explored pressure range. The azeotropic mole fraction increases in 1-propanol as pressure and/or temperature increases. For the case of interfacial tension, this binary mixture displays positive deviation from the linear behaviour and decreases as the 1-propanol liquid mole fraction increases.The reliability of the reported vapour – liquid equilibrium data is verified by the Fredenlund's consistency thermodynamic test, and the isobaric phase equilibria data are well-correlated by Margules, Wilson, NRTL, and UNIQUAC activity coefficients models, where the NRTL and UNIQUAC models provide the best fit. Finally, the measurements of the interfacial tension of the mixture are satisfactorily correlated by using three parameters of the Myers-Scott equation.

Multi-level delumping strategy for thermal enhanced oil recovery simulations at low pressure

We present a multi-level delumping method suitable for thermal enhanced oil recovery processes. At low pressures, the temperature variable is the most critical factor impacting the displacement process through viscosity reduction and evaporation/condensation effects. Hydrocarbon components are vaporized under high temperatures, move downstream in the gas phase and condense back to the liquid phase. That process is governed by the K-values of the components, evaporating out of the liquid phase sequentially with increasing temperatures. To reduce the computational cost, it is standard practice to reduce the number of (pseudo-) 6 components used in thermal reservoir simulation. Depending on the number and type of hydrocarbon pseudo-components retained in the simulations, we may not be able to capture the correct displacement due to large errors in the lumped phase behavior (flash) computations. We address that problem through a multi-level method: we use data obtained from a short simulation using the most detailed fluid description available, and leverage that information to guide a delumping process. We use temperature as a proxy variable for composition, and select reference temperatures. We extract the corresponding reference compositions from the detailed run and use them to extend the lumped pseudo-components to an approximate detailed composition. We compute the phase mole fractions as well as the gas compressibility factor. We test our method using six heavy oil samples, and under two different recovery processes: hot nitrogen injection and in-situ combustion (air injection and exothermic oxidation reactions). The average error on the liquid mole fraction is reduced by 4–12 times (depending on the oil samples) compared to the flash using pseudo-components, and the maximum error by 6–48 times. We illustrate that the method is amenable to manually adding more information about the physics of some oil samples. We also discuss how to efficiently pick the reference temperatures. For uniformly sampled temperatures (between a minimum and maximum temperature), we conduct a sensitivity study which led us to use six temperatures. We ran both local (Pattern Search, PS) and global (Particle Swarm Optimization, PSO) gradient-free optimization methods. PS is able to find the closest local minimum to the uniform set, giving a limited improvement of 6.5%. The known increased cost for PSO is worth the investment in at least one of the cases we considered, leading to a 67% improvement.

Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Methanol, Acetonitrile, and Dimethyl Sulfoxide: A Combined Study of Femtosecond Raman-Induced Kerr Effect Spectroscopy and Molecular Dynamics Simulations.

In this study, we examined the low-frequency spectra of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) mixtures with methanol (MeOH), acetonitrile (MeCN), and dimethyl sulfoxide (DMSO), which were obtained by femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and molecular dynamics (MD) simulations. In addition, we estimated the liquid properties of the mixtures, such as density ρ, surface tension γ, viscosity η, and electrical conductivity σ. The line shapes of the low-frequency Kerr spectra of the three [MOIm][BF4] mixture systems strongly depend on the mole fraction of the molecular liquid, XML. The spectral intensity increases with increasing XML of the [MOIm][BF4]/MeCN system but decreases for the [MOIm][BF4]/MeOH and [MOIm][BF4]/DMSO systems. These behaviors of the spectral intensities reasonably agree with the vibrational density-of-states spectra when the polarizability anisotropies of MeOH, MeCN, DMSO, and ion species are considered. The characteristic frequencies (first moments, M1) of the low-frequency spectra of the three mixture systems are almost insensitive at XML = 0-0.6. However, the frequencies vary mildly at XML = 0.6-0.9 and dramatically at XML = 0.9-1. The XML-dependent M1 in the Kerr spectra are well reproduced by the MD simulations. Plots of M1 versus bulk parameter, (γ/ρ)1/2, for the three mixture systems show that the mixtures at XML = 0-0.6 behave like aromatic cation-based ionic liquids (ILs), those at XML = 0.9-1 are molecular liquids (MLs), and those at XML = 0.6-0.9 are transitioning between aromatic cation-based ILs and MLs. MD simulations show that the solvent molecules localized at the interface between the ionic and the alkyl group regions without forming large solvent networks at XML = 0-0.6. However, solvent networks or regions develop largely at XML = 0.6-0.9 and the constituent ions of the IL disperse in the MLs at XML = 0.9-1. The MD simulations corroborate the results obtained by fs-RIKES.

Quantifying intermolecular interactions between 1‑Hexyl-3-methylimidazolium Nitrate and 1-alkanol: Internal pressure and cohesive energy density approach

For the binary mixtures of [Hmim][NO3] with (C6 to C10) 1-alkanol, values of cohesive energy density (ced), free volume (vf), and internal pressure (Pint) at 303.15 K and ambient pressure were calculated. To calculate the cohesive energy density and the internal pressure of the binary systems, the COSMO-RS model in combination with experimental densities, and Flory’s statistical theory was applied respectively. From the above results, the Pint/ced ratio was tested to study the ‘structuredness’ of fluids. Obtained values (0.2–0.8) are a feature of associated or ionic liquids and demonstrate the strong interactions in binary fluids. The variation of calculated parameters with the chain length of alcohols and the mole fraction of ionic liquid was considered from the standpoint of molecular interactions. It was found that increasing the alkyl chain of alcohol loosens the packing structure of binary liquids and reduces the strength of intermolecular forces.

Measurement, modelling and molecular dynamics analysis for isobaric vapour-liquid equilibria of binary or ternary system (diethylamine, ethyl acetate, triethylamine)

Diethylamine, ethyl acetate and triethylamine are usually applied to synthesize an important flame retardant of vinylphosphorus, which has high ability to retard flames, low toxic content, and good washing durability. The isobaric VLE data of (diethylamine + triethylamine, diethylamine + ethyl acetate) and (ethyl acetate + trimethylamine) system were determined at 101.3 kPa for industrial separation. A minimum azeotrope was discovered at x = 0.8217 in the (ethyl acetate + trimethylamine) system. Therefore, a series of experiments were designed to investigate the effect of diethylamine on the (ethyl acetate + trimethylamine) system and the results indicated that the azeotrope can be eliminated when the liquid mole fraction of diethylamine is greater than 0.4687. Furthermore, molecular dynamics analysis through GROMACS software and Multiwfn software was also used to study the interaction of these three materials in this work. The results show that the weak interaction force around ethyl acetate decreases after adding diethylamine, which means that the van der Waals effect and the electrostatic effect of ethyl acetate become smaller. This may be the main reason why the azeotropic point of the (ethyl acetate + trimethylamine) system disappears.

Estimation and Correlation of Phase Equilibrium of CO2–Hydrocarbon Systems with PRMHV2-UNIFAC and PRMHV2-NRTL Models

In this work, the Peng–Robinson (PR) equation of state (EoS) and MHV2 mixing rule that were combined with UNIFAC and NRTL GE models were used to predict vapor–liquid phase equilibrium (VLE) data for CO2–hydrocarbon systems. These systems included 12 binary systems and three ternary systems. The PRMHV2-UNIFAC model was used to calculate the bubble pressure, and the average absolute relative deviations (AARD %) were 17.49–32.20% for 12 binary systems. For the PRMHV2-NRTL model, the binary interaction parameters of the NRTL model dependent on temperature were regressed based on the binary VLE data. These new interaction parameters were used to estimate CO2–hydrocarbon VLE data for binary and ternary systems. The bubble pressure was predicted by the PRMHV2-NRTL model, and the AARD % values were 1.52–9.44% for binary systems, which were lower than the value of the PRMHV2-UNIFAC model. The PRMHV2-UNIFAC and PRMHV2-NRTL models were also used to calculate the liquid phase mole fraction of CO2–hydrocarbon ternary ...

Isobaric vapor-liquid equilibria for the extractive distillation of tert-butyl alcohol + water mixtures using 1-ethyl-3-methylimidazolium dicyanamide ionic liquid

Isobaric vapor-liquid equilibria for the binary systems tert-butyl alcohol + water, and tert-butyl alcohol + 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]), as well as the vapor-liquid equilibria for the tert-butyl alcohol + water + [emim][DCA] ternary system, have been obtained at 100 kPa using a recirculating still. The electrolyte nonrandom two-liquid (e-NRTL) model was successfully used for fitting the experimental data. The effect of [emim][DCA] on the tert-butyl alcohol + water system has been compared with that produced by other ionic liquids reported in the literature. From the results, [emim][DCA] appears as a good entrainer for the extractive distillation of this solvent mixture, causing the azeotrope to disappear at 100 kPa when the ionic liquid mole fraction is >0.095.

Modeling and Simulation of the Absorption of CO2 and NO2 from a Gas Mixture in a Membrane Contactor

The removal of undesirable compounds such as CO2 and NO2 from incineration and natural gas is essential because of their harmful influence on the atmosphere and on the reduction of natural gas heating value. The use of membrane contactor for the capture of the post-combustion NO2 and CO2 had been widely considered in the past decades. In this study, membrane contactor was used for the simultaneous absorption of CO2 and NO2 from a mixture of gas (5% CO2, 300 ppm NO2, balance N2) with aqueous sodium hydroxide solution. For the first time, a mathematical model was established for the simultaneous removal of the two undesired gas solutes (CO2, NO2) from flue gas using membrane contactor. The model considers the reaction rate, and radial and axial diffusion of both compounds. The model was verified and validated with experimental data and found to be in good agreement. The model was used to examine the effect of the flow rate of liquid, gas, and inlet solute mole fraction on the percent removal and molar flux of both impurity species. The results revealed that the effect of the liquid flow rate improves the percent removal of both compounds. A high inlet gas flow rate decreases the percent removal. It was possible to obtain the complete removal of both undesired compounds. The model was confirmed to be a dependable tool for the optimization of such process, and for similar systems.